Resource utilization of hazardous gypsum sludge in oxidation smelting of lead concentrate

Abstract

Gypsum sludge, a hazardous waste generated by the non-ferrous smelting industry, presents a significant challenge for disposal and utilization. To investigate the feasibility of substituting gypsum sludge for limestone as a flux for smelting, the effects of calcium sulfate (CaSO₄) and smelting conditions on oxygen-rich smelting of lead concentrate were studied. The interaction between CaSO₄ and sulfides facilitates the conversion of CaSO₄ into CaO, which is crucial for slag formation. The order of the influence of sulfide minerals on the conversion of CaSO₄ is pyrite > sphalerite > galena. When using gypsum sludge exclusively as the calcium source, under optimal conditions with a CaO/SiO₂ mass ratio of 0.8, an FeO/SiO₂ mass ratio of 1.2, a melting temperature of 1150 °C, an oxygen flow rate of 1.3 L/min, the recovery rates of Pb and Zn in the lead-rich slag reached 85.01% and 95.69%, respectively, with a sulfur content of 2.65 wt%. The As content in the smelting slag obtained by reduction smelting was 0.02 wt%. Resource utilization of gypsum sludge in lead smelting is a feasible method.

Keywords

gypsum sludge / calcium sulfate / resource utilization / smelting